os: support file systems without file IDs when reading directories on windows

Some file systems do not support file IDs. We should not use
FILE_ID_BOTH_DIR_INFO when reading directories on these file systems,
as it will fail. Instead, we should use FILE_ID_FULL_DIR_INFO,
which doesn't require file ID support.

Fixes #61907
Fixes #61918

Change-Id: I83d0a898f8eb254dffe5b8fc68a4ca4ef21c0d85
Reviewed-on: https://go-review.googlesource.com/c/go/+/518195
Run-TryBot: Quim Muntal <quimmuntal@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>

src/internal/syscall/windows/symlink_windows.go

@@ -9,6 +9,8 @@ import "syscall"
 const (
 	ERROR_INVALID_PARAMETER syscall.Errno = 87
 
+	FILE_SUPPORTS_OPEN_BY_FILE_ID = 0x01000000
+
 	// symlink support for CreateSymbolicLink() starting with Windows 10 (1703, v10.0.14972)
 	SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE = 0x2
 

src/internal/syscall/windows/syscall_windows.go

@@ -397,6 +397,21 @@ type FILE_ID_BOTH_DIR_INFO struct {
 	FileName        [1]uint16
 }
 
+type FILE_FULL_DIR_INFO struct {
+	NextEntryOffset uint32
+	FileIndex       uint32
+	CreationTime    syscall.Filetime
+	LastAccessTime  syscall.Filetime
+	LastWriteTime   syscall.Filetime
+	ChangeTime      syscall.Filetime
+	EndOfFile       uint64
+	AllocationSize  uint64
+	FileAttributes  uint32
+	FileNameLength  uint32
+	EaSize          uint32
+	FileName        [1]uint16
+}
+
 //sys	GetVolumeInformationByHandle(file syscall.Handle, volumeNameBuffer *uint16, volumeNameSize uint32, volumeNameSerialNumber *uint32, maximumComponentLength *uint32, fileSystemFlags *uint32, fileSystemNameBuffer *uint16, fileSystemNameSize uint32) (err error) = GetVolumeInformationByHandleW
 //sys	GetVolumeNameForVolumeMountPoint(volumeMountPoint *uint16, volumeName *uint16, bufferlength uint32) (err error) = GetVolumeNameForVolumeMountPointW
 

src/os/dir_windows.go

@@ -19,9 +19,11 @@ type dirInfo struct {
 	// buf is a slice pointer so the slice header
 	// does not escape to the heap when returning
 	// buf to dirBufPool.
-	buf  *[]byte // buffer for directory I/O
-	bufp int     // location of next record in buf
-	vol  uint32
+	buf   *[]byte // buffer for directory I/O
+	bufp  int     // location of next record in buf
+	vol   uint32
+	class uint32 // type of entries in buf
+	path  string // absolute directory path, empty if the file system supports FILE_ID_BOTH_DIR_INFO
 }
 
 const (
@@ -49,26 +51,47 @@ func (d *dirInfo) close() {
 	}
 }
 
+// allowReadDirFileID indicates whether File.readdir should try to use FILE_ID_BOTH_DIR_INFO
+// if the underlying file system supports it.
+// Useful for testing purposes.
+var allowReadDirFileID = true
+
 func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
 	// If this file has no dirinfo, create one.
-	var infoClass uint32 = windows.FileIdBothDirectoryInfo
 	if file.dirinfo == nil {
 		// vol is used by os.SameFile.
 		// It is safe to query it once and reuse the value.
 		// Hard links are not allowed to reference files in other volumes.
 		// Junctions and symbolic links can reference files and directories in other volumes,
 		// but the reparse point should still live in the parent volume.
-		var vol uint32
-		err = windows.GetVolumeInformationByHandle(file.pfd.Sysfd, nil, 0, &vol, nil, nil, nil, 0)
+		var vol, flags uint32
+		err = windows.GetVolumeInformationByHandle(file.pfd.Sysfd, nil, 0, &vol, nil, &flags, nil, 0)
 		runtime.KeepAlive(file)
 		if err != nil {
 			err = &PathError{Op: "readdir", Path: file.name, Err: err}
 			return
 		}
-		infoClass = windows.FileIdBothDirectoryRestartInfo
 		file.dirinfo = new(dirInfo)
 		file.dirinfo.buf = dirBufPool.Get().(*[]byte)
 		file.dirinfo.vol = vol
+		if allowReadDirFileID && flags&windows.FILE_SUPPORTS_OPEN_BY_FILE_ID != 0 {
+			file.dirinfo.class = windows.FileIdBothDirectoryRestartInfo
+		} else {
+			file.dirinfo.class = windows.FileFullDirectoryRestartInfo
+			// Set the directory path for use by os.SameFile, as it is possible that
+			// the file system supports retrieving the file ID using GetFileInformationByHandle.
+			file.dirinfo.path = file.name
+			if !isAbs(file.dirinfo.path) {
+				// If the path is relative, we need to convert it to an absolute path
+				// in case the current directory changes between this call and a
+				// call to os.SameFile.
+				file.dirinfo.path, err = syscall.FullPath(file.dirinfo.path)
+				if err != nil {
+					err = &PathError{Op: "readdir", Path: file.name, Err: err}
+					return
+				}
+			}
+		}
 	}
 	d := file.dirinfo
 	wantAll := n <= 0
@@ -78,13 +101,14 @@ func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []Di
 	for n != 0 {
 		// Refill the buffer if necessary
 		if d.bufp == 0 {
-			err = windows.GetFileInformationByHandleEx(file.pfd.Sysfd, infoClass, (*byte)(unsafe.Pointer(&(*d.buf)[0])), uint32(len(*d.buf)))
+			err = windows.GetFileInformationByHandleEx(file.pfd.Sysfd, d.class, (*byte)(unsafe.Pointer(&(*d.buf)[0])), uint32(len(*d.buf)))
 			runtime.KeepAlive(file)
 			if err != nil {
 				if err == syscall.ERROR_NO_MORE_FILES {
 					break
 				}
-				if infoClass == windows.FileIdBothDirectoryRestartInfo && err == syscall.ERROR_FILE_NOT_FOUND {
+				if err == syscall.ERROR_FILE_NOT_FOUND &&
+					(d.class == windows.FileIdBothDirectoryRestartInfo || d.class == windows.FileFullDirectoryRestartInfo) {
 					// GetFileInformationByHandleEx doesn't document the return error codes when the info class is FileIdBothDirectoryRestartInfo,
 					// but MS-FSA 2.1.5.6.3 [1] specifies that the underlying file system driver should return STATUS_NO_SUCH_FILE when
 					// reading an empty root directory, which is mapped to ERROR_FILE_NOT_FOUND by Windows.
@@ -103,18 +127,32 @@ func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []Di
 				}
 				return
 			}
-			infoClass = windows.FileIdBothDirectoryInfo
+			if d.class == windows.FileIdBothDirectoryRestartInfo {
+				d.class = windows.FileIdBothDirectoryInfo
+			} else if d.class == windows.FileFullDirectoryRestartInfo {
+				d.class = windows.FileFullDirectoryInfo
+			}
 		}
 		// Drain the buffer
 		var islast bool
 		for n != 0 && !islast {
-			info := (*windows.FILE_ID_BOTH_DIR_INFO)(unsafe.Pointer(&(*d.buf)[d.bufp]))
-			d.bufp += int(info.NextEntryOffset)
-			islast = info.NextEntryOffset == 0
+			var nextEntryOffset uint32
+			var nameslice []uint16
+			entry := unsafe.Pointer(&(*d.buf)[d.bufp])
+			if d.class == windows.FileIdBothDirectoryInfo {
+				info := (*windows.FILE_ID_BOTH_DIR_INFO)(entry)
+				nextEntryOffset = info.NextEntryOffset
+				nameslice = unsafe.Slice(&info.FileName[0], info.FileNameLength/2)
+			} else {
+				info := (*windows.FILE_FULL_DIR_INFO)(entry)
+				nextEntryOffset = info.NextEntryOffset
+				nameslice = unsafe.Slice(&info.FileName[0], info.FileNameLength/2)
+			}
+			d.bufp += int(nextEntryOffset)
+			islast = nextEntryOffset == 0
 			if islast {
 				d.bufp = 0
 			}
-			nameslice := unsafe.Slice(&info.FileName[0], info.FileNameLength/2)
 			name := syscall.UTF16ToString(nameslice)
 			if name == "." || name == ".." { // Useless names
 				continue
@@ -122,13 +160,19 @@ func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []Di
 			if mode == readdirName {
 				names = append(names, name)
 			} else {
-				f := newFileStatFromFileIDBothDirInfo(info)
+				var f *fileStat
+				if d.class == windows.FileIdBothDirectoryInfo {
+					f = newFileStatFromFileIDBothDirInfo((*windows.FILE_ID_BOTH_DIR_INFO)(entry))
+				} else {
+					f = newFileStatFromFileFullDirInfo((*windows.FILE_FULL_DIR_INFO)(entry))
+					// Defer appending the entry name to the parent directory path until
+					// it is really needed, to avoid allocating a string that may not be used.
+					// It is currently only used in os.SameFile.
+					f.appendNameToPath = true
+					f.path = d.path
+				}
 				f.name = name
 				f.vol = d.vol
-				// f.path is used by os.SameFile to decide if it needs
-				// to fetch vol, idxhi and idxlo. But these are already set,
-				// so set f.path to "" to prevent os.SameFile doing it again.
-				f.path = ""
 				if mode == readdirDirEntry {
 					dirents = append(dirents, dirEntry{f})
 				} else {

src/os/export_windows_test.go

@@ -7,8 +7,9 @@ package os
 // Export for testing.
 
 var (
-	FixLongPath       = fixLongPath
-	CanUseLongPaths   = canUseLongPaths
-	NewConsoleFile    = newConsoleFile
-	CommandLineToArgv = commandLineToArgv
+	FixLongPath        = fixLongPath
+	CanUseLongPaths    = canUseLongPaths
+	NewConsoleFile     = newConsoleFile
+	CommandLineToArgv  = commandLineToArgv
+	AllowReadDirFileID = &allowReadDirFileID
 )

src/os/os_windows_test.go

@@ -1524,3 +1524,73 @@ func TestNewFileInvalid(t *testing.T) {
 		t.Errorf("NewFile(InvalidHandle) got %v want nil", f)
 	}
 }
+
+func TestReadDirPipe(t *testing.T) {
+	dir := `\\.\pipe\`
+	fi, err := os.Stat(dir)
+	if err != nil || !fi.IsDir() {
+		t.Skipf("%s is not a directory", dir)
+	}
+	_, err = os.ReadDir(dir)
+	if err != nil {
+		t.Errorf("ReadDir(%q) = %v", dir, err)
+	}
+}
+
+func TestReadDirNoFileID(t *testing.T) {
+	*os.AllowReadDirFileID = false
+	defer func() { *os.AllowReadDirFileID = true }()
+
+	dir := t.TempDir()
+	pathA := filepath.Join(dir, "a")
+	pathB := filepath.Join(dir, "b")
+	if err := os.WriteFile(pathA, nil, 0666); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(pathB, nil, 0666); err != nil {
+		t.Fatal(err)
+	}
+
+	files, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(files) != 2 {
+		t.Fatalf("ReadDir(%q) = %v; want 2 files", dir, files)
+	}
+
+	// Check that os.SameFile works with files returned by os.ReadDir.
+	f1, err := files[0].Info()
+	if err != nil {
+		t.Fatal(err)
+	}
+	f2, err := files[1].Info()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !os.SameFile(f1, f1) {
+		t.Errorf("SameFile(%v, %v) = false; want true", f1, f1)
+	}
+	if !os.SameFile(f2, f2) {
+		t.Errorf("SameFile(%v, %v) = false; want true", f2, f2)
+	}
+	if os.SameFile(f1, f2) {
+		t.Errorf("SameFile(%v, %v) = true; want false", f1, f2)
+	}
+
+	// Check that os.SameFile works with a mix of os.ReadDir and os.Stat files.
+	f1s, err := os.Stat(pathA)
+	if err != nil {
+		t.Fatal(err)
+	}
+	f2s, err := os.Stat(pathB)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !os.SameFile(f1, f1s) {
+		t.Errorf("SameFile(%v, %v) = false; want true", f1, f1s)
+	}
+	if !os.SameFile(f2, f2s) {
+		t.Errorf("SameFile(%v, %v) = false; want true", f2, f2s)
+	}
+}

src/os/types_windows.go

@@ -32,10 +32,11 @@ type fileStat struct {
 
 	// used to implement SameFile
 	sync.Mutex
-	path  string
-	vol   uint32
-	idxhi uint32
-	idxlo uint32
+	path             string
+	vol              uint32
+	idxhi            uint32
+	idxlo            uint32
+	appendNameToPath bool
 }
 
 // newFileStatFromGetFileInformationByHandle calls GetFileInformationByHandle
@@ -99,6 +100,20 @@ func newFileStatFromFileIDBothDirInfo(d *windows.FILE_ID_BOTH_DIR_INFO) *fileSta
 	}
 }
 
+// newFileStatFromFileFullDirInfo copies all required information
+// from windows.FILE_FULL_DIR_INFO d into the newly created fileStat.
+func newFileStatFromFileFullDirInfo(d *windows.FILE_FULL_DIR_INFO) *fileStat {
+	return &fileStat{
+		FileAttributes: d.FileAttributes,
+		CreationTime:   d.CreationTime,
+		LastAccessTime: d.LastAccessTime,
+		LastWriteTime:  d.LastWriteTime,
+		FileSizeHigh:   uint32(d.EndOfFile >> 32),
+		FileSizeLow:    uint32(d.EndOfFile),
+		ReparseTag:     d.EaSize,
+	}
+}
+
 // newFileStatFromWin32finddata copies all required information
 // from syscall.Win32finddata d into the newly created fileStat.
 func newFileStatFromWin32finddata(d *syscall.Win32finddata) *fileStat {
@@ -198,7 +213,13 @@ func (fs *fileStat) loadFileId() error {
 		// already done
 		return nil
 	}
-	pathp, err := syscall.UTF16PtrFromString(fs.path)
+	var path string
+	if fs.appendNameToPath {
+		path = fixLongPath(fs.path + `\` + fs.name)
+	} else {
+		path = fs.path
+	}
+	pathp, err := syscall.UTF16PtrFromString(path)
 	if err != nil {
 		return err
 	}